[otrs] Language problem

Hi there.. Been using OTRS for a short while - absolutely fantastic ;-) I have a slight problem. When i click on any of the "compose answer (email)" options that i have setup, for certain users, the header and footer appear in German although I have the defaults set to english. I though this may be something to do with my customer accounts, but have checked that the users are set to use the english language. Any ideas?